//
// GTMNSObject+KeyValueObserving.h
//
// Copyright 2009 Google Inc.
//
// Licensed under the Apache License, Version 2.0 (the "License"); you may not
// use this file except in compliance with the License.  You may obtain a copy
// of the License at
//
// http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
// WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.  See the
// License for the specific language governing permissions and limitations under
// the License.
//

//
// MAKVONotificationCenter.h
// MAKVONotificationCenter
//
// Created by Michael Ash on 10/15/08.
//

// This code is based on code by Michael Ash.
// Please see his excellent writeup at
// http://www.mikeash.com/?page=pyblog/key-value-observing-done-right.html
// You may also be interested in this writeup:
// http://www.dribin.org/dave/blog/archives/2008/09/24/proper_kvo_usage/
// and the discussion on cocoa-dev that is linked to at the end of it.

#import <Foundation/Foundation.h>

#ifndef GTM_PERFORM_KVO_CHECKS
// Controls whether KVO checking code is on in debug. See
// GTMNSObject+KeyValueObserving.m for details
# define GTM_PERFORM_KVO_CHECKS 0
#endif

// If you read the articles above you will see that doing KVO correctly
// is actually pretty tricky, and that Apple's documentation may not be
// completely clear as to how things should be used. Use the methods below
// to make things a little easier instead of the stock addObserver,
// removeObserver methods.
// Selector should have the following signature:
// - (void)observeNotification:(GTMKeyValueChangeNotification *)notification
@interface NSObject (GTMKeyValueObservingAdditions)

// Use this instead of [NSObject addObserver:forKeyPath:options:context:]
-(void)gtm_addObserver:(id) observer
            forKeyPath:(NSString*)keyPath
              selector:(SEL) selector
              userInfo:(id) userInfo
               options:(NSKeyValueObservingOptions)options;
// Use this instead of [NSObject removeObserver:forKeyPath:]
-(void)gtm_removeObserver:(id) observer
               forKeyPath:(NSString*)keyPath
                 selector:(SEL)selector;

// Use this to have |self| stop observing all keypaths on all objects.
-(void)gtm_stopObservingAllKeyPaths;

@end

// This is the class that is sent to your notification selector as an
// argument.
@interface GTMKeyValueChangeNotification : NSObject<NSCopying> {
  @private
  NSString* keyPath_;
  id object_;
  id userInfo_;
  NSDictionary* change_;
}

-(NSString*)keyPath;
-(id)object;
-(id)userInfo;
-(NSDictionary*)change;
@end
